Multilayer Switches -- A Switch That Speed-Reads Mission-Critical Apps -- The Appswitch 2000 from Toplayer Networks packs custom chips that apply QOS to specific types of IP traffic.
Data Communications, April 7, 1999 p23(1)
By Reardon, Marguerite
Smarter is better, except when it's slower-and that's especially true of LAN switches. Now Toplayer has a multilayer switch that's clever and quick: It digs deep into Layer 7 information buried in packets to make sure business apps travel business class. And since the box is built around custom ASICs (application-specific integrated circuits), it can furnish full Layer 3 routing on all LAN and WAN ports at wire speed, according to the vendor.
But there are a few downsides. The switch routes IP only, costs more than the competition, and doesn't furnish gigabit Ethernet. What's more, since Toplayer Networks Inc. (Westborough, Mass.) has just started shipping the Appswitch, there's not much evidence on how well it performs on real-life nets.
Still, early tests indicate the product is acquitting itself well. "We've used it to shape traffic over our WAN links," says beta-tester Joe Turner, associate director of MIS for Fitchburg State College (Fitchburg, Mass.). "So far, the performance has been fine."
Picky About Protocols
The Appswitch 2000 has 14 10/100-Mbit/s ports, and links to the WAN via an optional module with two T1 and two V.90 modem ports. It can sit in front of a server, controlling access to certain apps. It can also sit in front of a router, shaping outgoing traffic onto the slower WAN-or act as a router itself (see the figure).
The Appswitch can differentiate among more than 100 different protocols and applications and prioritize traffic from certain end-users. It can also tell what transactions apps are performing and control those flows intelligently. For example, it could determine whether a user at an online store is buying or browsing. Then the net manager could define a policy that gives the buyer priority over the browser.
Appswitch relies on an embedded library to know how far it needs to look into the packets to identify an app. It stores traffic characteristics for such apps and protocols as FTP (file transfer protocol), HTTP (hypertext transfer protocol), Lotus Notes, Peoplesoft, Pointcast, POP (post office protocol) 3, SAP R/3, and telnet. For example, Appswitch can identify certain traffic as e-mail and then know where to look to determine the size of the message. Net managers can use this capability to define policies limiting bulk e-mails, which could keep the network from collapsing under the load. "One of my clients had a problem where a 10-Mbyte e-mail attachment was forwarded across the network 148 times. It crushed the application and the network," says Jim Finch, senior consultant for First Consulting Group Inc. (Long Beach, Calif.). Finch thinks the Appswitch could avert such disasters.
Trying to run such packet-probing devices on a typical platform would dampen performance. Not so with the Appswitch, says Toplayer. It claims its product blasts packets at wire speed. It's built the library of app characteristics into custom silicon, which speeds the process of sorting through apps as well as buffer management and address lookups, according to the vendor.
Competitive Edge
Toplayer's isn't the only multilayer switch out there. High-speed Layer 4 switches from Cabletron Systems Inc. (Rochester, N.H.) and Fore Systems Inc. (Warrendale, Pa.) can separate out HTTP traffic. And the Contentsmart load-balancing switch from Arrowpoint Communications Inc. (Westford, Mass.) uses URLs, considered Layer 7 information, to identify Web-enabled appls. But none of these can recognize as many apps or delve into as many Layer 7 details as Toplayer's box does.
Still, while boxes from competitors like Cabletron also route IPX, Toplayer's product only works with IP. And at $700 per 10/100-Mbit/s port and $3,995 for a WAN module, it's pricier than some competing gear. Cabletron's Smartswitch Router sells for $500 per 10/100-Mbit/s Ethernet port, with WAN modules at $1,625. Fore's goes for $585 per 10/100-Mbit/s Ethernet port. Finally, the Appswitch lacks the ability to handle gigabit Ethernet. |
